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Re: Rad Safe Blood Irradiator
I would check into the (1) the tube current to ensure
you are not having problems with the electrons. Then,
I would check out (2) target damage due to heat
loading.
Let me know what you learn.
--- "Smith, Laura T. (Physics)"
<Laura.Smith7@stjohn.org> wrote:
> Hello,
> I would like to request a RADSAFE brain trust on an
> issue we have with our Rad Safe Blood Irradiator.
>
> We purchased a New Rad Safe Blood Irradiator in 2001
> - which was at the time a new technology that uses
> an X-ray Tube versus the standard Cs-137 for
> irradiating Blood products. Below I have listed our
> service
> schedule, but the summary is every 6-12 months we
> are forced to increase the time the of irradiation
> due
> to our TLD dosimetry measurement falling below the
> required 2500cGy+_10% we require for our standard.
> The time has
> had to be increased to such a length that it will
> soon perhaps interfere with our duties and blood
> irradiation flow rate.
>
> The manufacturer says they are not sure what is
> causing this and are currently performing research
> to
> determine why time always needs increasing. My
> initial thought was flaking of the anode, causing a
> filter effect
> on the glass which continuous increases and filters
> out radiation, therefore taking longer to get to the
> 2500cGy
> value. The manufacturer says they do not think so
> based on research, but are unsure - they do not
> manufacturer the
> tubes and are in consult with the tube manufacturer.
>
>
> Other than the flaking of the anode theory, what
> might cause this?
>
> Laura Smith
>
>
>
> Date Issue TLD Dose Time
> 8/8/2001 New unit 2534
> 8/10/2001 independent evaluator 2734 6.4min
> 9.27/01 Dose check 2350 ""
> 10/19/01 Qtrly Dose Check 2660 ""
> 1/24/02 "" 2610 ""
> 5/24/02 "" 2460 ""
> 7/12/02 "" 2440 "" - time increased
> 10/10/02 time increased check again 2460 6.8
> 12/26/02 Annual service contract 2360 6.8
> 1/15/03 Qtrly Dose Check 2190 6.8 - time
> increased
> 2/4/03 time increased check again 2530 7.5
> 4/7/03 Qtrly Dose Check 2360 7.5 - time
> increased
> 7/9/03 time increase check again 2460 8.1
>
>
>
>
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=====
"Self-criticism is the secret weapon of democracy, and candor and confession are good for the public soul."
Adlai Stevenson
-- John
John Jacobus, MS
Certified Health Physicist
e-mail: crispy_bird@yahoo.com
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